1. Technical Field
This invention relates generally to electrostatographic copying and/or printing machines, and more particularly to the maintenance of high image quality in the presence of changes in the ratio of toner particle electrostatic charge to toner particle mass (the charge-to-mass ratio).
2. Background Art
In electrostatographic machines such as printers and copiers, image contrast, density, and color balance can be adjusted by changing certain process control parameters, including toner concentration of the development mixture, primary voltage "V.sub.0 ", bias voltage transfer voltage, and exposure. " For a detailed explanation of the theory of copier contrast and exposure control by controlling various process control parameters, reference may be made to the following article: Paxton, Electrophotographic Systems Solid Area Response Model, 22 Photographic Science and Engineering 150 (May/June 1978).
Generally in process control, a test patch or patches are imaged and developed on non-image areas of the transfer member. By feedback processes, abnormal toner density readings of the patches result in adjustments to at least one of the process control parameters to thereby return the density readings toward normal values.
Developed density is also a function of the ratio of the charge-to-mass ratio of the toner). As the charge-to-mass ratio increases, developed toner density decreases for a given potential difference in the development zone.